58
Distance protection (ZM)
Chapter 4
Line distance
1.2
Functionality
Separate digital signal processors calculate the impedance as seen for different measuring loops
in different distance protection zones. The results are updated each millisecond, separately for
all measuring loops and each distance protection zone. Measurement of the impedance for each
loop follows the differential equation, which considers complete line replica impedance, as pre-
sented schematically in
figure 16
.
Figure 16:
Schematic presentation of impedance measuring principle.
Settings of all line parameters, such as positive sequence resistance and reactance as well as ze-
ro-sequence resistance and reactance, together with expected fault resistance for phase-to-phase
and phase-to-earth faults, are independent for each zone. The operating characteristic is thus au-
tomatically adjusted to the line characteristic angle, if the simplified operating characteristic has
not been especially requested. The earth-return compensation factor for the earth-fault measure-
ment is calculated automatically by the terminal itself.
Voltage polarization for directional measurement uses continuous calculation and updating of
the positive sequence voltage for each measuring loop separately. This secures correct direction-
ality of the protection at different evolving faults within the complex network configurations. A
memory retaining the pre-fault positive-sequence voltage secures reliable directional operation
at close-up three-phase faults.
Where:
R
l
= line resistance
R
f
= fault resistance
X
l
= line reactance
ω
= 2
π
f
f
= frequency
u t
( )
R
l
R
f
+
(
)
i t
( )
X
l
ω
-----
Δ
i t
( )
Δ
t
------------
⋅
+
⋅
=
R
l
jX
l
R
f
u(t)
i(t)
98000063.vmf
Summary of Contents for REL 501-C1 2.5
Page 1: ...Technical reference manual Line distance protection terminal REL 501 C1 2 5 ...
Page 2: ......
Page 26: ...14 Introduction to the technical reference manual Chapter 1 Introduction ...
Page 42: ...30 Technical data Chapter 2 General ...
Page 66: ...54 Blocking of signals during test BST Chapter 3 Common functions ...
Page 142: ...130 Time delayed overvoltage protection TOV Chapter 6 Voltage ...
Page 162: ...150 Autorecloser AR Chapter 9 Control ...
Page 174: ...162 Event function EV Chapter 10 Logic ...
Page 210: ...198 Serial communication Chapter 12 Data communication ...
Page 226: ...214 Serial communication modules SCM Chapter 13 Hardware modules ...
Page 230: ...218 Terminal diagrams Chapter 14 Diagrams Figure 87 REL 501 C1 with DC switch ...
Page 234: ...222 Terminal diagrams Chapter 14 Diagrams ...
Page 237: ......